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A Decaheme Cytochrome as a Molecular Electron Conduit in Dye-Sensitized Photoanodes.

Hwang ET, Sheikh K, Orchard KL, Hojo D, Radu V, Lee CY, Ainsworth E, Lockwood C, Gross MA, Adschiri T, Reisner E, Butt JN, Jeuken LJ - Adv Funct Mater (2015)

Bottom Line: The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP).The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM).Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, University of Leeds Leeds, LS2 9JT, UK E-mail: L.J.C.Jeuken@leeds.ac.uk ; The Astbury Centre for Structural Molecular Biology, University of Leeds Leeds, LS2 9JT, UK.

ABSTRACT

In nature, charge recombination in light-harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye-sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR-1, where the 10 hemes of MtrC form a ≈7-nm-long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction-band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems.

No MeSH data available.


Related in: MedlinePlus

CV at 1 V s−1 and 20 °C before (gray) and after (black) adsorption of MtrC onto a 8-OH/8-NH3+ (ratio of 80/20) modified gold electrode in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4). The insert shows the baseline-subtracted protein signal.
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fig04: CV at 1 V s−1 and 20 °C before (gray) and after (black) adsorption of MtrC onto a 8-OH/8-NH3+ (ratio of 80/20) modified gold electrode in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4). The insert shows the baseline-subtracted protein signal.

Mentions: To optimize construction of the photoanode composed of RuP-TiO2 and MtrC on a gold electrode, ultra-flat template-stripped gold surfaces were modified with a range of different self-assembled monolayers (SAMs), made up of various mixtures of alkanethiols with positive (amine), negative (carboxylic acid), and uncharged (hydroxyl) “headgroups.” A dilute MtrC protein solution (<1 × 10−6m) was applied to the surface for 1 min at 20 °C after which non-bound MtrC was removed by rinsing with buffer. The purity of MtrC was confirmed with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and UV–vis electronic absorption spectroscopy (Figure S4, Supporting Information). Cyclic voltammetry (CV) was used to compare the electroactive coverage of MtrC on the various surfaces and the SAM composition was found to influence this property significantly. Redox signals were only detected with positively charged surfaces and the highest electroactive coverage was obtained with a SAM consisting of 8-mercaptooctanol (8-OH) and 8-amino-1-octanethiol (8-NH3+) in an 80/20 ratio (Figure4). At neutral pH, MtrC has an overall negative charge and the positively charged SAM is expected to interact favorably with the negatively charged propionate groups of the c-type hemes, facilitating the desired orientation in which MtrC can directly exchange electrons with the electrode.


A Decaheme Cytochrome as a Molecular Electron Conduit in Dye-Sensitized Photoanodes.

Hwang ET, Sheikh K, Orchard KL, Hojo D, Radu V, Lee CY, Ainsworth E, Lockwood C, Gross MA, Adschiri T, Reisner E, Butt JN, Jeuken LJ - Adv Funct Mater (2015)

CV at 1 V s−1 and 20 °C before (gray) and after (black) adsorption of MtrC onto a 8-OH/8-NH3+ (ratio of 80/20) modified gold electrode in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4). The insert shows the baseline-subtracted protein signal.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493899&req=5

fig04: CV at 1 V s−1 and 20 °C before (gray) and after (black) adsorption of MtrC onto a 8-OH/8-NH3+ (ratio of 80/20) modified gold electrode in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4). The insert shows the baseline-subtracted protein signal.
Mentions: To optimize construction of the photoanode composed of RuP-TiO2 and MtrC on a gold electrode, ultra-flat template-stripped gold surfaces were modified with a range of different self-assembled monolayers (SAMs), made up of various mixtures of alkanethiols with positive (amine), negative (carboxylic acid), and uncharged (hydroxyl) “headgroups.” A dilute MtrC protein solution (<1 × 10−6m) was applied to the surface for 1 min at 20 °C after which non-bound MtrC was removed by rinsing with buffer. The purity of MtrC was confirmed with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and UV–vis electronic absorption spectroscopy (Figure S4, Supporting Information). Cyclic voltammetry (CV) was used to compare the electroactive coverage of MtrC on the various surfaces and the SAM composition was found to influence this property significantly. Redox signals were only detected with positively charged surfaces and the highest electroactive coverage was obtained with a SAM consisting of 8-mercaptooctanol (8-OH) and 8-amino-1-octanethiol (8-NH3+) in an 80/20 ratio (Figure4). At neutral pH, MtrC has an overall negative charge and the positively charged SAM is expected to interact favorably with the negatively charged propionate groups of the c-type hemes, facilitating the desired orientation in which MtrC can directly exchange electrons with the electrode.

Bottom Line: The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP).The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM).Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, University of Leeds Leeds, LS2 9JT, UK E-mail: L.J.C.Jeuken@leeds.ac.uk ; The Astbury Centre for Structural Molecular Biology, University of Leeds Leeds, LS2 9JT, UK.

ABSTRACT

In nature, charge recombination in light-harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye-sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR-1, where the 10 hemes of MtrC form a ≈7-nm-long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction-band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems.

No MeSH data available.


Related in: MedlinePlus